1. Field of the Invention
This invention relates to a cassette for holding a roll of web material, the cassette having a housing with two side walls, and on each side wall of the housing a cylindrical bearing to support in a rotatable manner a core of the roll and, in particular, with at least one friction brake, which has at least one spring element that, in a relaxed position, projects into an open cross-section of the roll.
2. Description of Related Art
U.S. Pat. No. 3,944,148 discloses a cassette having a cylindrical housing of synthetic resin with side walls from which protrude cylinder segments that support on their outer surfaces a core of a roll of copying paper. A conical extension of one cylinder segment contains a shaped wire ring that engages this extension with three radially oriented tabs through circumferential slits and fits spring-like into the core. When the web material is unwound from the roll, some friction results, originating from the core rubbing against the cylinder segments and from the spring contact between the wire spring and the core, thus preventing an undesirable unrolling or back rotation of the roll. The bearing and friction relationships are different from one roll to another, because neither the core, which generally consists of cardboard, nor the wire spring are manufactured with adequate precision.
Similar cassettes of this type, but without friction brakes, are also known for rolls of photographic web material, either film or paper, for various purposes, such as portrait photography, photo typesetting, x-ray photography and the like. The cassettes are constructed to be lightproof. In one type of cassette, a cuboid or cylindrical housing wall is provided on each of the two side walls with a locking plate supporting a cylindrical bearing. In a second type of commercial cassette, two injection-molded half shells are bonded together along a diagonal juncture line to form a cuboid housing. Each half shell has a half of a bearing socket on each side wall.
It is believed desirable to make a cassette in which better defined bearing and friction relationships are attainable in a simple manner.